Means for lapping split workpieces

ABSTRACT

APPARATUS IS PROVIDED BY WHICH OPPOSING FACES OF A SPLIT WORKPIECE MAY BE LAPPED READILY TO A FACE-TO-FACE FIT. THE WORKPIECE IS HELD BY THE APPARATUS IN A FIXED POSITION WITH A LAPPING BLADE INSERTED BETWEEN THE OPPOSING FACES OF THE SPLIT AND RECIPROCATED. THE LAPPING BLADE IS SHAPED SO THAT UPON INSERTION IT CONTACTS THE RESPECTIVE FACES OF THE SPLIT IN A RELATION THAT CORRESPONDS TO THE FACE-TO-FACE FIT DESIRED, AND THE BLADE IS ARRANGED FOR RECIPROCATION SO THAT IT IS ALWAYS FREE TO FIND AN ALIGNED POSITION BETWEEN THE OPPOSING FACES BEING LAPPED, AND SO THAT IT IS ALWAYS PULLED DURING THE RECIPROCATION.

Jan. 19, 1971 w, L ET AL 3,555,738

MEANS FOR LAPPING SPLIT WORKPIECES Filed March 28, 1969 '4 Sheets-Sheet l INVENTORS FRANK w. NEAL &

ROBERT L. SNYDER ATTORN Y5 Jan. 19, 1971 w, NEAL ET AL 3,555,738

MEANS FOR LAPPING SPLI'i WORKPIECES Filed March 28, 1969 4 SheetsSheet' 2 INVENTORS mum w. mm a BY ROBERT L. .snraan 'ATTOF'QNE s Jan. 19', 1971 w, NEAL ETAL 3,555,738

MEANS FOR LAPPING SPLIT WORKPIECES Filed March 28, 1969 4 Sheets-Sheet :5

IN VENTORS FRANK m NEAL a BY ROBfiRT L. sums? ATTGR EVS Jan. 19, 1971 w, NEAL ET AL 3,555,738

' MEANS FOR LAPPING SPLIT WORKPIECES Filed March 28, 1969 4 Sheets-Sheet 4 INVENTORS FRANK W IVE/IL 6' R08Rr L. SNYDQR CA z. 6%.4, E- $AJ 7/. 54.42;

ATTOQNC Y8 United States Patent 3,555,738 MEANS FOR LAPPING SPLIT WORKPIECES Frank W. Neal and Robert L. Snyder, Charlotte, NC,

assignors to R. H. Bouligny, Inc., Charlotte, N.C., a

corporation of North Carolina Filed Mar. 28, 1969, Ser. No. 812,579

- Int. Cl. B24b 7/00 US. Cl. 51-,59 Claims ABSTRACT OF THE DISCLOSURE Apparatus is provided by which opposing faces of a split workpiece may be lapped readily to a face-to-face fit. The workpiece is held by the apparatus in a fixed position with a lapping blade inserted between the opposing faces of the split and reciprocated. The lapping blade is shaped so that upon insertion it contacts the respective faces of the split in a relation that corresponds to the face-to-face fit ,desired; and the blade is arranged for reciprocation so that it is always free to find an aligned position between the opposing faces being lapped, and so that it is always pulled during the reciprocation.

BACKGROUND OF THE INVENTION A problem has persisted over the years with the excessive hand labor required in forming the split rings used to seal the breechblock juncture in artillery pieces. These split rings are used to form a gastight seal between the firing chamber and the breechblock, and they are split so: that they will expand to a gastight seating under firing pressure. The splits are formed diagonally in the rings to allow for this expansion while providing relatively extended faces at the split for opposing contact, and it is necessary that these opposing faces of the split have a fine face-to-face fit in order to maintain the rings gastight at this point.

Fitting of the split faces is commonly done by hand lapping which is not only slow and tedious but also requires a degree of skill that is difiicult to recruit and maintain satisfied in the face of the exacting demands of this operation. U.S. Pat. No. 2,401,279 contains a prior art proposal for mechanizing the lapping operation, but this proposal was apparently unsuccessful for hand lapping still persists as the practice in common use.

It appears likely that failure of the above-noted prior art proposal to replace the hand lapping procedure was due principally to a failure to see the necessity for lapping the respective split faces mechanically in a relation that corresponds to the face-to-face fit required, although other aspects of the apparatus suggested by this previous proposal have serious practical disadvantages as well.

The present invention providesmeans for lapping the split rings that is now being used to eliminate the hand lapping entirely.

SUMMARY OF THE INVENTION The lapping means provided by the present invention comprises a fixed means for supporting the split rings with the split therein positioned for lapping; a lapping blade shaped for inserting between the opposing faces of the split so that the respective split faces are contacted by the blade in a relation that:corresponds to the relation that must be assumed by the faces when face-to-face; a holder for the lapping blade; and a reciprocably mounted carrier for the blade holder; the carrier and holder being respectively arranged so that the latter is always free when carried by the former to allow the held lapping blade to find an aligned position between the opposing split faces being lapped, and so that the latter and the 3,555,738 Patented Jan. 19, 1971 ice held lapping blade are always pulled upon reciprocation DESCRIPTION OF THE DRAWINGS FIG. 1 is a side elevation of means embodying the present invention for lapping the opposing split faces of I the previously mentioned split rings;

FIG. 2 is a plan view corresponding to FIG. 1;

FIG. 3is a right-side view of the work support superstructure as seen from the position 33 in FIG. 2;

FIG. 4 is a sectional detail of the lapping blade and blade holder taken at the line 4-4 in FIG. 1;

FIG. 5 is a plan view of a split ring such as is lapped by the means of the present invention;

FIG. 6 is a sectional detail taken at the line 6-6 in FIG. 5; and

FIG. 7 is a bottom side view corresponding to FIG. 5.

DESCRIPTION OF THE PREFERRED EMBODIMENT In the illustrated embodiment a base plate is designated by the reference numeral 10 on which the several apparatus elements are positioned.

The work support, indicated generally by the reference numeral 12, is held on the base plate 10 by clamp pieces 14 bolted in place to grip the support 12 at a fixed disposition, while allowing it to be removed readily for replacement by a counterpart whenever a different size of split ring R must be handled.

The clamp pieces 14 grip edge portion 16 of a work support base structure 18 that rises to provide an elevated table surface at 20 on which a superstructure 22 is bolted at an angled disposition to hold the split ring R for lapping. The split ring R is held at an upright front plate portion 24 of the superstructure 22 that is braced by gussets 26 at its back face and has its front face fitted with a jig piece 28 and with top and side clamps 30 and 32. The jig piece 28 has curved end portions 28' and 28" that fit the inner diameter of the split ring R for locating purposes, and it is arranged at the right side of the front plate 24, opposite the side clamp 32, so that a split ring R positioned around its end portions 28' and 28" will extend within the reach of both the top and side clamps 30 and 32.

A split ring R is installed on the front plate 24 for lapping, as seen in FIG. 1, with the square edge of its split S disposed vertically, or substantially so, and downwardly opposite the top clamp 30. Both of the top and side clamps 30 and 32 are fitted with clamp screws 30" and 32' operable by hand to tighten them on the installed split ring Ryand the side clamp 32 has an upwardly extending arm portion 32" bolted at its extending end to the front plate-24 to maintain this clamp in position for such tightening.

The work support superstructure 22 additionally carries a presser bar 34 at the right edge of the front plate 24, which is pivoted at its upper end on a stud 36 and is backed at its lower end by a cam roll 38 that is carried at an eccentric axis 40 and provided with an operating lever 42 (as seen best in FIG. 3). Movement of this operating lever 42 to the right from its upstanding FIG. 3 position causes the cam roll to bias the pressure bar 34 outwardly about its pivot stud 36 and thereby press the overlying portion of the split ring R, adjacent the jig piece 28, outwardly as well to force the split S open for the lapping purpose that will be noted presently. Before passing from the work support superstructure 22, however, it should also be noted that a further jig bracket 44 is bolted in place at 46 behind the front plate 24 and extends around the presser bar 34 to carry an adjustable positioning screw 48 for use in holding thesplit'ring seated on the jig piece 28 during installation. i

Use of the presser bar 34 to force the split S open in the above-noted manner allows insertion of a lapping blade 50 between the opposing faces of the split in preparation for the lapping operation. The lapping blade 50 is formed (see FIG. 4) by a rigid base element 52 having an abrasive sheet 54 folded thereover and clamped together with the base element 52 on /holder 56 by a clamping bar 58 bolted to the holder 56.

The base element 52 of the lapping blade 50 is specially shaped with a tapered cross section, so that the lapping blade portion extending from the holder 50 between the opposing faces of the ring split S will establish lapping contact with these faces in a relation that corresponds to the parallel face-to-face relation which-the faces must assume when the lapping blade 50 is removed. The particular taper employed will depend primarily on the size of split ring R being handled, and different base elements 52 must be employed for each ring size, but the proper taper can be empirical y determined quite readily in each instance to lap the split faces with exceptional accuracy.

Once the lapping blade 50 has been inserted between the opposing faces of the split S, the operating lever 42 is released to remove the opening bias imposed through the presser bar 34 and allow closing of the split faces on the lapping blade 50. When this happens the split faces will bear oppositely on the lap-ping blade 50 to urge it toward an aligned disposition, and the blade holder 56 is arranged to allow this alignment to take place. For this purpose, the blade holder 56 is fitted with hanger pol.- tions 60 at each end from which trunnions 62 extend to rest freely in horizontal slots 64 of spaced supporting arm portions 66 rising from a carrier 68. By this arrangement, the holder 56 and held lapping blade 50v are always maintained free to swing about the trunnions 62 to find the vertical alignment urged by the opposing faces of the split S, and to assume the dictated longitudinal alignment as well through responsive lateral shifting of the studs 62 in the slots 64.

The carrier 68 is reciprocably mounted on a crosshead 70 supported by a pillow block 72 bolted to the base plate 10. Mounting of the carrier 68 on the crosshead 70 is provided for at a stub rod 74 extending from a post member 76 on the carrier 68 to enter a bore 78 'in'the adjacent end of the crosshead 70. The stub rod 74 -is shouldered for penetration of the crosshead bore 78 to a fixed extent, and is circumferentiallygrooved toward its extending end for engagement by a set screw 80 installed in the crosshead 70.

The other end of the crosshead 70 hasa connecting rod 82 pivoted thereat which extends from a crank-plate 84 carried on a shaft 86 that is mounted in further pillow blocks 88 on the base plate for driving-from a motor '90 also mounted on the base plate 10. Operation of the motor 90 consequently results in ultimate reciprocation of the lapping blade 50 to cause lapping of the opposing split faces between which it is disposed, and it should be noted in particular that the lapping blade 50 is'always pulled during this reciprocation by reasonof the fitting of each blade holder trunnion 62 with a washer 9-2 and backing pin 94 to provide shoulder means in shortly spaced relation beyond the spaced supporting arm por tions 66 of the carrier 68, so that upon each -reversal of the reciprocating movement the carrier 68 engages the blade holder 56 at the end disposed'forwardly in the direction of reciprocation to'pull the lapping blade 50 and thereby eliminate any tendency for"itto"buckle 'd'tTr'-' ing any phase of the lapping operation.

The foregoing embodiment of the lapping means' of the present invention is employed in the course of forma; a split 'rin Ramblin After rough machining a solid ring to serve as a blank for the split ring R, this blank is heat treated and then specially reheated for a local twisting to introduce a fkink that stresses the blanlgto .impose a, closing sprfing-lilge, bias at t he, :split S afferit is c ut, as noted inutlie ipreviously mentioned ULS. .P.jat.,l Io, 2,411,279. The diagonal split S is then cut in the blank with an abrasivesaw at a position located in 180 relationeto.thefkink, sowthat the-imposed bias is applied in a balanced manner to urge the opposing facesof the cut split together. i

At this point, a first lapping operation is performed to 3 give the split faces an initial fit. A lapping blade 50 of selected taper for 'the" size of iirigR b eing' liandled is employed,--.and .the kink -bias maintains both faces of the split in contact with .theblade 50 as the operation pnoceeds. .At this first lapping operation, however," the saw .cutwill have left the ,opposing split faces somewhat out of parallelin their closed position, and the abrasive sheet ..54,employed. in the,,lapping blade 50 at thiscst-age. is therefore .a relatively coarsev emery cloth capableof working the split faces: roughly. intoparallel relation with aeoarser finish than is-ultirnately required. I

,,When.-.a n initial fit has thusbeen obtained at the split S, it is soldered so asto be held as if itwere solidwhile the ring R is given a semi-finish machining all over, after which the solder is removed by heating and a second lapping operation isremployed, this time with a relatively must'be reached'quite precisely.

the s plit- S and cleaningit.

fine emery cloth to begin the finish lapping of the split faces'fThis second lap is again followed" by soldering of the split' S and-afur'the'r semi-finish machining of the ring R all over to work it closer to the final dimensions'that Then the solder is r'emoved"from the split S 'a'gain by heatingand it is subjected to a third' and final lapping operationto finish 'the 'face to-face fit of the" split faces",

before'a finish "machiningand grinding "of the ring R all over, "and a-deburring and chrome plating, all with the split S again soldered fastfiThefinished ring R is' then subjected toan inspection'while held solid by the solder, and to a final inspection after removing the solder from f. i j e alafi st s v es i f h f ft e g'oiiig"procedure are"performed byihancl at least 15 thiniit es fis'required' for 'the first, 3.0 minutes for the second step ,'and an :houri'for thejthi'rd, even when" the requisite skill is steadily-applied; The practical fact of the matter,

however, is' that it 'is' exceedi'ngly 'difiicult"to' keep requisite and sliill available" or these -lap'jpin'g' steps so that the "s'up'e'rvisiorf"necessar'y' to maintain theharid lap: Plug in? reasonable tep with the: procedure as a wholeis unduly burdensomeeven when successful g1 In contrast, the lapping-means-ofthe present invention allows'the fir'stdaiiping step to be performed readilydnffi' minutes, and the" secoifd and third stepsin about 4 minutes; with r'egu'larly consist'ent results; "When a batch of split rings R 'o'fa given siie is "to be processed, the propertaper for-the lapping blade 50""is' selected at each lapping step by first trying the blade taper that prior 'exper iencehas indicated as likely to-be suitable, Azlapped; ring R is then inspected by applying a bluing coat to one face of the split S and-observing rtheimpression obtained on the other face.

lfthe impression obtained is not satisfactory,- a blade 50=ofdifierent taper is substitutedand the-rifigR is'lapped again and inspected until'the proper relationofthe split faces 'lappifigresults." a

:While slight "diiferences ii'n physical characteristics or L treatment of the'rin'gs'R from batch to batch'wil-l'often' require adjustment'o'f the 'la'ppingfblade' taper 'to suit each batch, not more than one adjustment-is ordinarily required after'alittle experience' batsmen-gained as to'thefiikely taper .needed for a gi ven sizeringzFqr the"- size rangeofsplitfrings R normally em loyed have used'-blades I 50rangin'g taperto .0133 inch/inch in steps usually of .001 inch/inch.

And as a greater taper is needed as the diameter of the ring becomes smaller, it soon becomes possible to select the proper taper for a given ring size quite closely.

In providing lapping blades of different taper, it is preferable to maintain the tip of the base element 52 on which the taper is formed at a constant width so that the superimposed abrasive sheet will fold over all of the base elements in comparable fashion. We have used a tip width dimension of .031 for our base elements 52, which are formed from flat ground steel stock X 2" x 9".

The abrasive sheet 54 is suitably Metallite emery cloth as supplied by the Norton Company. This emer cloth may be obtained in 50' rolls of 4" strip so that pieces are cut readily to fit the above-noted base element 52, and is formed with aluminum oxide grit installed on a lightweight cloth backing by a resin bond that stands up well under pressure. For the first lapping step we use a grade designated at 100X that bears a grit yielding a finish in the order of to microinches, while the 240X grade is employed for the second and third lapping steps to provide a grit yielding a finish in the 15 to 20 microinch range. A new piece of emery cloth is installed for lapping each ring R, which may be readily done with lapping blade arrangement employed in our lapping means, and a timing device (not shown) is preferably used to control the lapping period for each ring R.

Standard specifications for split rings R of the sort being considered here require a minimum contact area between the faces of the split S. With the lapping means of the present invention it is possible to produce a contact area at the second and third lapping steps with consistent ease.

The present invention has been described in detail above for purposes of illustration onl and is not intended to be limited by this description or otherwise to exclude any variation or equivalent arrangement that would be apparent from, or reasonably suggested by, the foregoing disclosure to the skill of the art.

What is claimed is:

1. Apparatus for lapping opposing faces of a split workpiece to a face-to-face fit comprising fixed means for supporting said workpiece with the split thereof positioned for lapping the opposing faces thereat, a lapping blade shaped for insertion between said opposing faces in a relation to the respective faces that corresponds to the face-to-face fit desired, a holder for said lapping blade, and a reciprocably mounted carrier for said holder, said carrier and holder being respectively arranged so that the latter is always free when carried by the former to allow the held lapping blade to find an aligned position between said opposing workpiece faces and so that the latter and the held lapping blade are always pulled upon reciprocation of the former.

2. Apparatus as defined in claim 1 and further characterized in that said fixed supporting means is equipped with selectively operable biasing means for forcing said opposing workpiece portions apart to allow insertion of said lapping blade therebetween.

3. Apparatus as defined in claim 1 and further characterized in that said workpiece is ring-shaped, in that the split is diagonally formed in said workpiece, and in that said lapping blade has a transverse cross section that is tapered at the degree necessary for lapping the respective faces of said split in a relation that will render said faces parallel when said lapping blade is removed.

4. Apparatus as defined in claim 1 and further characterized in that said holder is formed for releasably clamping said lapping blade, and in that said lapping blade is formed by a rigid base element and an abrasive sheet folded thereover for clamping together with said base element in said holder.

5. Apparatus as defined in claim 1 and further characterized in that said carrier has spaced supporting arm portions that are horizontally slotted, and in that said holder has trunnions extending at each end to rest freely in said supporting arm slots and extend therethrough with shoulder means fitted to said trunnions in shortly spaced relation beyond said supporting arm portions.

References Cited UNITED STATES PATENTS 2,401,279 5/1946 Thorndike 29156.62X

WILLIAM R. ARMSTRONG, Primary Examiner US. Cl. X.R. 5l324, 328 

